If `f(x)=[x]`, where [x] is the greatest integer not greater than x, in (-4, 4), then `f(x)` is
A. discontinuous at `x=0`, only in (-4, 4)
B. continuous at `x=0` only in (-4,4)
C. discontinuous at every integral point of (-4,4)
D. continuous at every integral point of (-4,4)
